Digital broadcasting refers to the broadcasting service that provides users with high-definition, high-fidelity and high-quality broadcastings, in replacement of the conventional analog broadcasting. With the recent development of the digital broadcasting and mobile communication technologies, there is an increasing interest in the study for allowing the users to view the digital broadcasting even while traveling by a vehicle or walking.
Such digital broadcasting is serviced by Digital Multimedia Broadcasting (DMB). For example, in South Korea, DMB is classified into satellite DMB which is serviced throughout the country on a charge basis, and terrestrial DMB which is serviced in the capital area including Seoul on a free-of-charge basis. In IEEE 802.16-based Wireless Broadband (WiBro) or Mobile Worldwide Interoperability for Microwave Access (Mobile WiMAX), IEEE 802.11-based Wireless LAN, and 3rd Generation (3G), intensive discussions are being held on Broadcasting/Communication Convergence in which the digital broadcasting services are available over the communication networks, such as Wideband Code Division Multiple Access (WCDMA), Universal Mobile Telecommunications System (UMTS) and High Speed Downlink Packet Access (HSDPA) by the 3rd Generation Partnership Project (3GPP) group, and CDMA 2000, 1x Evolution Data Only (EVDO) and 1x Evolution Data and Voice (EVDV) by the 3rd Generation Partnership Project 2 (3GPP2) group.
Under the assumption that the above heterogeneous networks coexist, consideration is given to the scheme capable of supporting the networks by means of dual-mode terminals, each of which is equipped with separate modems capable of receiving services of the networks. Actually, a product made by realizing DMB and WiBro in a single terminal is under the study.
Therefore, when one terminal receives the digital broadcasting service in the heterogeneous network environment where the multiple networks coexist, it is important for the terminal to know how to access each network and communicate with it in providing effective, economical broadcasting service to the user. In particular, the broadcasting service should be provided such that the user may view all broadcasting program content without missing any, even when a moving terminal can no longer receive the broadcasting service if it enters a no-service area (such as a shadow area) while the user views the broadcasting program.
Nevertheless, conventionally, there is no detailed method in which a moving terminal can seamlessly access the heterogeneous networks and communicate with them at a low price when the moving terminal is disconnected from the terrestrial or satellite DMB network as it enters an area where it cannot receive the digital broadcasting service. In particular, no consideration is given to the method in which even though the terminal receives again the digital broadcasting service as it moves back to the DMB service area after a lapse of a predetermined time, the user can conveniently view his or her missing broadcasting content.